Tires and Suspension

Your car’s tires, suspension, and steering gear are designed to all work together so that you can keep the vehicle under control. The suspension in particular is what’s between your tires (the vehicle’s only contact with the pavement) and the frame and body, playing a crucial part in your ride comfort, control, and ability to maneuver and negotiate turns. If your suspension parts (shock absorbers, struts, springs, bushings) are starting to wear out or are damaged, an uncomfortable ride might be the least of your problems. Suspension problems can cause tires to wear prematurely and can affect your safety while driving.

What is car suspension?

Put simply, the suspension parts are what controls vertical motion when you hit a bump or an irregularity in pavement. They also keep the vehicle from leaning excessively due to momentum when you go around a corner, or from drastically nose-diving when you hit the brakes and inertia shifts the vehicle’s weight forward. Suspensions go back as far as 18th-century coaches and wagons, which had primitive spring systems to make the ride a little less bone-jarring for passengers.

Suspensions for front wheels and rear wheels are usually designed quite a bit differently from each other, due to the weight distribution of a vehicle and the fact that front wheels are subject to a different set of forces when cornering or braking.

As far as your car is concerned, automakers put a lot of thought into designing a suspension that’s integral with the tires and steering mechanism for a compromise between ride quality and handling. Stiffer shocks and springs often mean a vehicle will corner and handle exceptionally well, but at the expense of a harsher ride. On the other hand, if you’ve ever driven a car from the 60s or 70s, you probably noticed that the ride was very forgiving and smooth, but the vehicle’s handling was pretty imprecise and felt almost disconnected from the steering wheel.

What can happen if car suspension is bad?

If your suspension is starting to wear out or has damaged parts, you might notice that the car feels “squirrely” on the highway and that cornering and handling are uncertain. Shock absorbers in particular are designed to damp up-and-down movement; a vehicle with worn shocks might continue to bounce several times after hitting a bump or pothole, resulting in a queasy ride for driver and passengers.

Worn suspension parts mean more than an uncomfortable ride; they can make your vehicle downright dangerous to drive and can affect control.

How does car suspension affect tires?

Let’s say that your shocks are starting to wear out and can’t arrest vertical motion after hitting a bump or pothole. When things get to that point, your tires can actually lose contact with the road completely for a moment, resulting in “cupped” wear to the tires. This “cupped” wear is usually irregular on the tread; newer vehicles with more advanced suspension designs may just display premature wear from worn shocks and not necessarily a cupped pattern.

Other suspension parts include tie rod ends, ball joints, control arms, control arm bushings, the Pitman arm and wheel bearings. Excessive wear on any of these can mean tires that are worn sporadically and maybe not with any specific wear pattern. If any of these parts are worn on your vehicle, you’ll notice that handling and road manners have become pretty sloppy, with excessive play in the steering. The ball joint in particular is what connects crucial front-end components, keeping the vehicle’s frame from just crashing to the pavement. A bad ball joint is dangerous and can result in loss of control if it fails completely.

How does steering and wheel alignment affect tires

As we mentioned above, the steering mechanism and suspension work together to deliver good control, ride quality, and handling. Your vehicle leaves the factory with the front wheels set to specific angles designed by the engineers for the best possible handling, ride and road manners. Steering parts can wear out or be damaged, causing the front wheels to deviate from factory specs. This can include:

• Toe-in: Toe-in is when a front wheel is pointed inwards, as seen from the top (imagine someone who walks “pigeon-toed”)
• Toe-out: This, of course, is the opposite of toe-in (think of someone who walks with one foot skewed out to the side)
• Caster: Caster is the fore-and-aft orientation of a wheel and tire on the vehicle
• Camber: Camber refers to the angle of the tire as viewed from the front. If the top of the wheel is angled inward, that’s referred to as negative camber; positive camber is if the top of the wheel is angled outward.

In the case of toe-in or toe-out, you’d have a situation where the tire in question is trying to steer the vehicle in a different direction as you head down the road. That tire then gets dragged along as you maintain the vehicle in a straight line, resulting in a constant pull where you have to hold the steering wheel off-center to keep from drifting to one side. That drag will result in the inside or outside edge of the tread being scrubbed off and wearing prematurely.

Other signs of wheel alignment problems include:

• Steering feels “heavy” or clumsy
• Steering wheel doesn’t easily re-center itself after rounding a corner
• Constant squeal from a tire while driving in a straight line
• Vibration through the steering wheel (although there can be other causes for this)

If you suspect a wheel alignment problem, an alignment shop can put the car on a rack where the angles are all examined carefully. From there, a technician can make adjustments to bring the vehicle’s alignment back into spec again. To give you an idea of how important these angles are, if your vehicle’s alignment was off by ⅛” and you went down the road for one mile on flat, un-crowned pavement with no correction, hands off the steering wheel, you’d end up roughly 28 feet off of that straight line (in the ditch or in the median, in other words).

How to adjust your suspension for best tire performance

Tire, suspension and steering maintenance are just as important as keeping your engine and transmission properly maintained. That includes:

• Regularly having the condition of the shocks, struts, bushings and connectors inspected – this is best done when the vehicle’s oil is being changed and the technician can get a good look underneath.
• Be on the lookout for signs of poor wheel alignment; unless front-end components are severely worn-out, an alignment is usually good for a long time unless you sustain a hard hit on a pothole, curb or railroad tracks.
• Have the steering parts inspected regularly – on high-mileage vehicles, things like ball joints, tie rod ends, Pitman arm and all the related connectors and bushings can wear to a point where there’s so much slop that the front end can’t be brought back into alignment and actually stay within spec.
• Be aware of any signs of worn shock absorbers/struts. This could include excessive bouncing after hitting a bump, clunks and creaks, and excessive lean while rounding a corner. One good way to test is to push down on the vehicle’s front end or rear end four or five times – the rebound should be one and a half bounces at most, and anything more than that could indicate shocks that are worn.

Tips for keeping your tires in good condition

Like we mentioned above, your tires and suspension should be just as important a part of routine maintenance as your vehicle’s engine and drivetrain. Out of all the things you can do to extend the life of your tires and keep them in good shape, regular tire rotations are probably the single most important thing.

Why are tire rotations so important? Your front tires are under a completely different set of forces and stresses than the vehicle’s rear tires. Braking and cornering shift the vehicle’s weight forward due to inertia, and the weight of the engine is over the front wheels as well. Regular tire rotations (at an interval of 5000-7000 miles) are the best way to ensure that all four tires wear evenly. After a tire rotation, you’ll probably notice an immediate difference in your vehicle’s handling, drivability and road manners. It’s also worth noting here that failure to rotate tires will result in a voided tire warranty. Most tire dealers include lifetime wheel balance and rotation for the entire service life of the tires, so you’d be wise to take advantage of that.

Other things to be mindful of include:

• Proper tire inflation, since underinflated tires will wear prematurely, begin to degrade due to excessive heat and rolling resistance, and affect handling and braking performance. Poor tire inflation can lead to complete tire failure at highway speed, and increased fuel economy due to rolling resistance. A tire can lose a pound or two of inflation pressure over the course of a month. When checking inflation or re-inflating, be sure to do so when tires are cold, since air expands when heated and your reading may be off.
• Regularly inspect your tires for damage and uneven wear. Keep an eye out for edge wear that can point to poor alignment, and lightly run a hand over the tread to feel for a “sawtooth” pattern that can point to front-end problems. Keep an eye out for sidewall bulges or tread separation, both of which are signs of a tire that needs to be replaced right away.
• Every tire rotation should also come with a wheel-balancing check. Wheel balance is done by mounting small lead weights to specific places on the rim, but as a tire wears down the mass of rubber decreases and a tire can go out of balance. Wheel balance issues can result in vibration or shimmy, sometimes only at specific speed ranges. In extreme cases, that vibration or shimmy can cause parts such as wheel bearings to wear prematurely.
• Inspect your tires for foreign objects and debris such as broken glass or nails in the tread. A small puncture can be fixable, but a puncture in the sidewall or shoulder can’t.